The third-ranking member of the Colombo crime family is facing an 18-to-24-month prison stint after pleading guilty yesterday to a shakedown scheme designed to cover another mobster’s medical bills after a stabbing.

Richard Fusco, 75, admitted that he joined in a health-care reform “sit-down” of Colombo leaders.

At the meeting — which was secretly taped by a mob turncoat — it was agreed that the Gambino crime family would pay the injured mobster’s bills because a Gambino had done the stabbing.

Most of the $150,000 tab was to come from the Gambinos’ illegally skimmed cut of proceeds from the annual Figli di Santa Rosalia celebration on 18th Avenue in Brooklyn, federal prosecutors said.

In the end, the injured wiseguy, Colombo associate Walter Samperi, never saw a penny, and sought subsidized health care in his native Italy.

Fusco’s guilty plea — and a similar action by family underboss Benjamin “The Claw’’ Castellazzo this month — threatens to jail two of the three highest-ranking Colombos for several years, yet another blow to a crime family weakened by Brooklyn federal prosecutions and the FBI.